First-degree relatives of individuals with RA are 2 – 3-times more likely to develop the disease . However , disease concordance in monozygotic twins is only 15 – 20 %, suggesting that non-genetic factors also play an important role . 5 , 6
Clinical presentation , course , prognosis Early RA starts with joint pain and stiffness in a few joints , typically wrists , fingers ( metacarpophalangeal joints and proximal interphalangeal joints ) and feet , accompanied by swelling .
Clinically visible arthritis is preceded by a preclinical stage (‘ preclinical RA ’) that is characterised by non-specific musculoskeletal symptoms and immunological changes , e . g ., circulating anti-cyclic citrullinated protein antibody ( ACPA ). These symptoms and antibodies can precede the onset of clinically detectable arthritis by months or years . 6
As the disease progresses , there is joint inflammation and swelling with progressive articular deterioration and deformities of the joints . Inevitably this leads to difficulties with the activities of daily living .
Established RA may be accompanied by several extraarticular disease manifestations such as interstitial lung disease , pleural effusion , fibrosing alveolitis , neuropathy , rheumatoid nodules and vasculitis .
The overall mortality in patients with RA is reportedly 2.5-times higher than that of the general age-matched population . 5
Features Genetic susceptibility plays an important role in the development of RA . 7 Genetic factors account for about 50 % of the risk for developing RA . 5 The presence of HLA DRB1 * 01 and HLA DRB1 * 04 , ( alleles of the HLA antigen D related ( DR ) locus ) are strongly associated with the risk of developing RA . 6
Current thinking suggests that RA develops when a genetically susceptible individual is exposed to an external factor ( e . g ., cigarette smoking , inhaled particles or infection ) that triggers an autoimmune reaction . 5 Among these factors , tobacco has the strongest evidence , especially in patients with positive RA-related autoantibodies . 5 Interestingly , alcohol has repeatedly been shown to have a protective effect .
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Female sex hormones may have a beneficial role as shown by the fact that the disease improves during pregnancy ; 5 this is tempered by the fact that RA is more prevalent in women .
Ankylosing spondylitis Ankylosing spondylitis ( AS ) is a condition which mainly affects the spine and sacroiliac joints and is characterised by the presence of sacroiliac joint changes on x-ray . 7
Axial inflammatory involvement can also be detected on magnetic resonance imaging in the absence of x-ray changes and this ( when other clinical features are present ) is classified as non-radiographic axial spondyloarthritis . The two conditions have similar presentations . 7
Incidence / prevalence The prevalence of AS is believed to range from 0.05 % to 0.23 % and is more common in men . 7
Clinical presentation , course , prognosis AS generally starts in early adulthood , most commonly between the ages of 20 and 30 years . The clinical course of the disease often involves persistent or fluctuating axial inflammation and structural progression . Patients with AS complain of back pain and stiffness with inflammatory characteristics ( worse after rest , e . g ., in the morning , better with movement ).
Complications include ankylosis ( spinal fusion ), spinal fractures , osteoporosis , hip joint damage ( requiring replacement ), anterior uveitis ( iritis ) and cardiac complications .
The resulting damage is progressive and irreversible and affects the patient ’ s quality of life and productivity due to pain , reduction in mobility and function . 7
Features Genetic susceptibility plays an important role in the development of AS , the most important risk factor being the HLA-B27 antigen . Environmental triggers for AS include infections and alterations to the host microbiome .
Smoking is also an important risk factor . It is also associated with increased severity of disease and more rapid radiological progression . 8
The defining feature of AS is sacroiliac joint inflammation leading to damage and ultimately fusion . In the spine , the formation of syndesmophytes ( bony growths in intervertebral joint ligaments ) can also lead to joint fusion .
There is a strong association between AS , inflammatory bowel disease and psoriasis .
Psoriatic arthritis Psoriatic arthritis ( PsA ) is a seronegative arthritis that occurs in approximately 20 % of people with psoriasis . 9 In the majority of patients ( 60 – 80 %), psoriasis precedes the onset of arthritis more rarely arthritis may precede psoriasis .
Incidence / prevalence The overall prevalence of PsA is 0.25 %; however , the rate is estimated to be between 5 % and 30 % amongst people with psoriasis . 9
Clinical presentation , course , prognosis The pathogenesis of PsA is still not fully understood . As with other inflammatory arthritides , genetic susceptibility , environmental factors , and immune-mediated inflammation all contribute to the development of this condition . However , the way in which these factors interact to produce the clinical picture is not fully known . A number of sub-types have been
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